JP2007523460A - Micro structure and manufacturing method thereof - Google Patents

Abstract

  Disclosed are a fuel cell, a fuel cell membrane, a micro fuel cell, and a method for producing them. Particularly typical fuel cells have a membrane containing materials such as organic conductive materials, inorganic conductive materials, and combinations thereof. The thickness of this film is about 0.01 to 10 μm, and the sheet resistance is about 0.1 to 1000 Ωcm 2.

Description

Priority claim based on related applications This application is filed in co-pending US Provisional Patent Application No. 60 / 545,772 filed Feb. 19, 2004 (invention entitled “Thin-Film Brains For Fuel Cells”). The entire contents of the above application are incorporated herein by reference.

Federal Government-sponsored research or development oath The US government shall have a lump sum license for this invention and, in certain circumstances, as determined by the US government DARPA (Grant # F33615-011-21-2173) Based on the MDA clause, the patentee can be asked to enter into a license agreement over a reasonable period of time to the other.

TECHNICAL FIELD The present invention relates generally to fuel cells, and more particularly to fuel cell membranes and micro fuel cells, and methods of manufacturing fuel cell membranes and micro fuel cells.

Background Portable electronic devices such as mobile communication devices, microsensors, microelectromechanical systems (MEMS), and microfluidic disk devices benefit from advances in energy storage technology. With the availability of power sources with higher energy density and lower prices, applications and functions can be broadened. One possible high energy density power source is a fuel cell.

  For electronic devices with low power requirements, research on microfabricated power sources including fuel cells is ongoing. Issues to consider include reducing size and weight, improving interconnect integrity with fewer interconnects, increasing processing efficiency, and lowering costs.

  Examples of the fuel for the device micro fuel cell include hydrogen, methanol, and other hydrocarbons (for example, ethylene glycol or formic acid). Hydrogen fuel cells and direct reaction fuel cells (DMFC) operate at relatively low temperatures (eg, ambient temperature to 120 ° C.). These fuel cells use a solid proton exchange membrane (PEM) to transfer protons from the anode to the cathode. Hydrogen can be stored as a pressurized gas or in the form of a metal hydride. In this case, it is necessary to perform humidification to increase the conductivity of the film.

  The methanol-water mixture can be oxidized at the anode in either liquid or vapor form. Methanol is an attractive fuel because it can be stored as a liquid, is inexpensive, and has a high specific energy. The liquid supply type DMFC is relatively simple compared to other fuel cell systems and can be easily downsized. The reason is that such a DMFC does not require a fuel reformer and does not require a complex humidifier or thermal management system. In addition, methanol has a higher energy density than lithium polymer batteries and lithium ion polymer batteries.

  Proton exchange membranes can also be used in low temperature fuel cells that operate with either hydrogen or methanol. The solid proton exchange membrane in conventional fuel cells is usually a perfluorinated polymer with side chains terminating in a non-sulfonic acid moiety such as Nafion ™. The membrane of a PEM fuel cell generally contains water to keep the conductivity high. If methanol passes through the membrane, a mixed potential is generated, the action of the oxygen reduction reaction is impaired, and the performance deteriorates. Accordingly, there is a need in the art to eliminate at least some of the shortcomings described above.

Brief Description of the Invention Briefly described, the present specification describes a fuel cell, a fuel cell membrane, a micro fuel cell, and a method of manufacturing each of these. Among them, a typical fuel cell has a membrane including a material such as an organic conductive material, an inorganic conductive material, or a combination thereof. The thickness of the film is about 0.01 to 10 μm, and the sheet resistance is about 0.1 to 1000 Ωcm ² .

A particularly typical micro fuel cell is a substrate on which an anode current collector is disposed and a film disposed on the anode current collector, the film comprising silicon dioxide, doped silicon dioxide, silicon nitride, oxynitriding. A material selected from silicon, metal oxides, metal nitrides, metal oxynitrides and combinations thereof, the thickness of the film is about 0.01 to 10 μm, and the area resistance of the film is about 0; A hollow channel substantially defined by the membrane of 1 to 1000 Ωcm ² , a portion of the substrate and a portion of the membrane, wherein at least one catalyst layer is exposed to the channel The anode current collector is a microchannel having the hollow channel disposed adjacent to the channel, and a cathode current collector disposed on the opposite side of the membrane from the substrate side. A charge batteries, fuel cells conductive path is present between the catalyst layer and the anode current collector.

  A method for manufacturing a micro fuel cell is also provided. In particular, a typical method for manufacturing a micro fuel cell includes a step of providing a substrate on which an anode current collector is arranged, a step of arranging a sacrificial polymer layer on the substrate and the anode current collector, and an arrangement on the anode current collector. Removing a sacrificial material in a portion not formed, forming a sacrificial material portion, disposing a first porous catalyst layer on the sacrificial material portion, the sacrificial material portion and the first porous catalyst layer; And a step of disposing a layer of membrane material over the anode current collector, removing the sacrificial material portion, and substantially defining the substrate, the membrane material, and the first porous catalyst layer. Forming a hollow channel formed. The film material includes a material selected from silicon dioxide, doped silicon dioxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, metal oxynitride, and combinations thereof.

  Another particularly representative manufacturing method includes providing a substrate having an anode current collector disposed thereon, disposing a sacrificial polymer layer on the substrate and the anode current collector, and disposing the substrate on the anode current collector. Removing a sacrificial polymer material in a portion that is not present, forming a sacrificial material portion, disposing a first porous catalyst layer on the sacrificial material portion, the sacrificial material portion, and the first porous catalyst layer And a layer of film material overlying the anode current collector, the film material comprising silicon dioxide, doped silicon dioxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, The step of including a metal oxynitride and a combination thereof, and removing the sacrificial material portion to substantially define the substrate, the membrane material, and the first porous catalyst layer. And a step of forming a hollow channels.

  Still another typical manufacturing method includes a step of providing a substrate on which an anode current collector and a catalyst layer are disposed, the anode current collector and the catalyst layer being adjacent to each other, and the substrate, the anode current collector. And a step of disposing a sacrificial polymer layer on the catalyst layer; removing a portion of the sacrificial polymer material not disposed on the anode current collector to form a sacrificial material portion on the catalyst layer; and Disposing a layer of film material over a material portion and the anode current collector, wherein the film material is silicon dioxide, doped silicon dioxide, silicon nitride, silicon oxynitride, metal oxide, metal nitride, metal Removing the sacrificial material portion to include the oxynitride and a combination thereof, and removing the sacrificial material portion into the substrate, the film material, and the catalyst layer. Ri and a step of forming a hollow channel substantially as picture made.

  Other structures, systems, methods, features and advantages will become apparent to those skilled in the art by reference to the drawings and detailed description. All such additional structures, systems, methods, features and advantages are intended to be within the scope of the present invention and protected by the following claims.

  Many aspects of the invention can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. Moreover, corresponding parts are designated by the same reference numerals throughout the several views.

DETAILED DESCRIPTION Fuel cell membranes, micro fuel cells, and methods of manufacturing the same are generally disclosed. The fuel cell membrane in the embodiment of the present invention is formed from silicon dioxide and / or doped silicon dioxide, and has a relatively thin and sheet resistance comparable to a thick polymer membrane. . The thinner the membrane, the easier it is for protons to pass through, so the amount of current that can be generated can be increased. In addition, the materials used to form these membranes, compared with currently used proton exchange membranes (PEMs), prevent the passage of reactants through the membrane, which is a common problem of direct reaction fuel cells. It is excellent in that point. Furthermore, these films can be manufactured using well-known manufacturing techniques for microelectronic devices. In this respect, the membrane can be manufactured on the structure of a microelectronic device intended for use in fuel cells.

  In one example, the fuel cell membrane and the micro fuel cell can be directly integrated into the electronic device. For example, the fuel cell membrane and the micro fuel cell are arranged by arranging the fuel cell membrane or the micro fuel cell on a chip, integrating the fuel cell membrane or the micro fuel cell on a substrate or a printed circuit board, and the fuel cell membrane. Alternatively, they can be integrated by interposing or mounting the micro fuel cell on the chip as an independent part coupled to the chip.

  In general, technical fields in which fuel cell membranes and micro fuel cells can be used include microelectronic devices (for example, microprocessor chips, communication chips and optoelectronic chips), microelectromechanical systems (MEMS), microfluidics, , Sensors, analyzers (eg, microchromatography), communication / positioning devices (eg, beacons and GPS systems), and recording devices, but are not limited thereto.

FIG. 1 is a cross-sectional view of a typical fuel cell membrane 10a. The fuel cell membrane 10a has a membrane 12 (that is, a membrane layer), and catalyst layers 14a and 14b are disposed on both sides of the membrane 12. As shown in FIG. 1, the fuel (eg, H ₂ , methanol, formic acid, ethylene glycol, ethanol, and combinations thereof) is one side of the fuel cell membrane 10a (eg, the anode side of the membrane (not shown)). In contrast, air contacts the opposite side of the fuel cell membrane 10a (eg, the cathode side of the membrane (not shown)). For example, when methanol is used, the following reaction occurs on each of the anode side and the cathode side of the fuel cell membrane.
H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O

  This film may include materials such as organic conductive materials and inorganic conductive materials, but is not limited thereto. Materials that can be included in the film include, for example, silicon dioxide, doped silicon dioxide, silicon nitride, doped silicon nitride, silicon oxynitride, doped silicon oxynitride, metal oxides (eg, titanium oxide, tungsten oxide), metal There are, but are not limited to, nitrides (eg titanium nitride), doped metal oxides, metal oxynitrides (eg titanium oxynitride), doped metal oxynitrides and combinations thereof. Generally, the film can be doped with about 0.1-20% dopant in the film with about 0.1-5% dopant.

  Doped silicon dioxide can include, but is not limited to, phosphorus-doped silicon dioxide, boron-doped silicon dioxide, aluminum-doped silicon dioxide, arsenic-doped silicon dioxide, and combinations thereof. Is not to be done. In general, doping causes atomic scale defects such as M-OH (M is a metal), which distorts the lattice and allows protons to be transported therethrough. The doping amount is 2 to 5% by weight of the dopant in the film so that the dopant in the film is 0.5 to 10% by weight so that the dopant in the film is 0.1 to 20% by weight. Can be.

  The thickness of the film 12 is about 10 μm or less, and is about 0.01 to 10 μm, about 0.1 to 5 μm, about 0.1 to 2 μm, about 0.5 to 1.5 μm, and about 1 μm. The length of the film 12 can be about 0.001 m to 100 m, and the width of the film 12 can be about 1 μm to 1000 μm. Note that the length and width of the membrane is application dependent and can be adjusted accordingly.

Sheet resistance of the film 12 is about 0.1～1000Omucm ^2, about 0.1 to 100 ^2, about 0.1～10Omucm ^2, about 1～100Omucm ² and about 1~10Ωcm ^2. The area resistance is defined as a resistance (for example, resistance × area or resistance × thickness) straddling a film in a region exposed to fuel.

  The film 12 can be formed using, but not limited to, spin coating, plasma enhanced chemical vapor deposition (PECVD), screen printing, doctor blade, spray coating, roller coating, meniscus coating, and combinations thereof. is not.

  Catalyst layers 14a and 14b can include, but are not limited to, catalysts such as platinum, platinum / ruthenium, nickel, palladium, alloys thereof, and combinations of each. In general, platinum catalysts are used in examples where the fuel is hydrogen, and platinum / ruthenium catalysts are used in other examples where the fuel is methanol. These catalyst layers 14a and 14b may contain the same catalyst or different catalysts. These catalyst layers 14a and 14b are typically porous catalyst layers that allow protons to pass through the porous catalyst layer. In addition, there is a conductive path between the catalyst layer and the anode current collector.

  The thickness of the catalyst layers 14a and 14b can be 1 μm or less, about 0.01 to 100 μm, 0.1 to 5 μm, and about 0.3 to 1 μm.

  The catalyst layers 14a and 14b can be formed by alternately layering the catalyst and the membrane material to form thicker catalyst layers 14a and 14b (for example, two or more layers). For example, the two-layer structure improves the fuel oxidation rate. This is advantageous because it can increase the anode catalyst loading and keep the catalyst layer porous. Since the surface area is large, the oxidation rate of the fuel can be increased. Higher speed means more current and power can be obtained.

  The film can be further subjected to post-doping treatment. Ionic conductivity can be increased by diffusing or embedding dopant in the film. Examples of the dopant include, but are not limited to, boron and phosphorus. Each dopant can be diffused into the membrane alone from a liquid source or a solid source, or can be ion implanted using a high pressure ion accelerator. The conductivity of the membrane can be increased by diffusing acidic compounds (eg, carboxylic acids (in the form of acetic acid and trifluoroacetic acid)) or inorganic acids such as phosphoric acid and sulfuric acid into the membrane.

  FIG. 2 is a cross-sectional view of a typical fuel cell membrane 10b. The fuel cell membrane 10b includes a composite membrane 18 and catalyst layers 14a and 14b. The composite film 18 has two film layers 12 and 16 (polymer layer 16). In another example, the fuel cell membrane 10b can be provided with three or more layers. One catalyst layer 14 a is disposed on the polymer layer 16, and the other catalyst layer 14 b is disposed on the membrane layer 12. The membrane layer 12 and the catalyst layers 14a and 14b are the same as those described with reference to FIG. The operation of the fuel cell membrane 10b is the same as or similar to that described above.

  Although the membrane layer 12 and the polymer layer 16 are independent layers, both of them operate as a fuel cell membrane. This combination of properties in the bilayer membrane (eg, ionic conductivity, fuel passage resistance, mechanical strength, etc.) can be superior to using each of these layers alone in some cases. For example, the polymer layer 16 can provide additional mechanical support and stability to the membrane layer 12.

  Further, in the example where the membrane layer 12 is silicon dioxide, this material is similar to other insulators used to fabricate the device, for example when the membrane 12 is used with a semiconductor device.

  Polymers that can be included in the polymer layer 16 include, but are not limited to, Nafion ™ (perfluorosulfonic acid / polytetrafluoroethylene copolymer), polyphenylenesulfonic acid, modified polyimide, and combinations thereof. Is not to be done. For example, using Nafion as the polymer layer 16 has been shown to increase the open circuit potential without compromising the current density, thereby increasing the power density and efficiency.

The thickness of the polymer layer 16 is about 1-50 μm, 5-50 μm and 10-50 μm. The length of the polymer layer 16 can be about 0.01 m to 100 m, and the width of the polymer layer 16 can be about 1 μm to 500 μm. Note that the length and width of the membrane is application dependent and can be adjusted accordingly. The polymer can be deposited using techniques such as, but not limited to, spin coating, so that the substrate can be completely covered by the polymer or in the desired area. It can also be selectively deposited.
The sheet resistance of the polymer layer 16 is about 0.001 to 0.5 Ωcm ² .

  3A-3D show four examples of micro fuel cells 20a, 20b, 20c and 20d. 3A shows a membrane 28, a substrate 22, an anode current collector 24, a cathode current collector 26, a first porous catalyst layer 14a, a second catalyst layer 14b, and three channels 32a, 32b and 32c. The micro fuel cell 20a which has is shown. The chemical composition, dimensions, and characteristics of the membrane 28 may be similar to those described above with respect to the membrane 12 with reference to FIG. The thickness of the film 28 is measured from the top of the channels 32a, 32b and 32c.

  The substrate 22 can be used in a system such as a microprocessor chip, a microfluidic device, a sensor, an analysis device, and a combination thereof, but is not limited thereto. Thus, the substrate 22 can be formed from a material suitable for the envisaged system (eg, an epoxy board can be used for a printed circuit board). Typical materials include glass, silicon, silicon compounds, germanium, germanium compounds, gallium, gallium compounds, indium, indium compounds, other semiconductor materials and / or compounds, and combinations thereof. However, the present invention is not limited to this. In addition, the substrate 12 can include non-semiconductor substrate materials, such as any dielectric material, metals (eg, copper and aluminum), ceramics, or organic materials used in printed circuit boards. Furthermore, the substrate 22 may include one or more specific components used in a certain system described above.

  The first porous catalyst layer 14a is disposed on the bottom surface close to the substrate 22 side of the membrane. The second porous catalyst layer 14b is disposed on the top surface of the membrane opposite to the substrate 22 side. The micro fuel cell 20a includes the first porous catalyst layer 14a and the second porous catalyst layer 14b, which form conductive paths to the anode current collector 24 and the cathode current collector 26, respectively. Yes. The first porous catalyst layer 14a and the second porous catalyst layer 14b include the same catalyst as described above, and can have the same thickness and characteristics.

  The anode current collector 24 collects electrons through the first porous catalyst layer 14a. The anode current collector 24 may include, but is not limited to, platinum, gold, silver, palladium, aluminum, nickel, carbon, their respective alloys, and combinations thereof.

  The cathode current collector 26 emits electrons. Cathode current collector 26 may include, but is not limited to, platinum, gold, silver, palladium, aluminum, nickel, carbon, their respective alloys, and combinations thereof.

  Depending on the desired configuration, various anode current collectors 24 and cathode current collectors 26 can be electrically connected in series or in parallel (eg, wired from anode to cathode (in series), or from anode to anode). Can also be wired in parallel). In one example, individual micro fuel cells can be electrically connected in series to form a stack of fuel cells to increase the output voltage. In another example, the output current at the rated voltage can be increased by connecting in parallel.

  Substantially the membrane 28, the first porous catalyst layer 14a and the substrate 22 define the channels 32a, 32b and 32c (for example, boundaries are formed on all sides of the cross-sectional view). Fuel (for example, hydrogen and methanol) is flowed through these channels and acts with the first porous catalyst layer 14a as described above. These channels 32a, 32b and 32c can be configured in series or in parallel, or a combination of these. The anode current collector 24 is disposed adjacent to the channels 32a, 32b and 32c, but is electrically connected to the porous catalyst layer 14a.

  In one example, the channels 32a, 32b and 32c are formed by removing (eg, degrading) the sacrificial polymer layer from the region where the channels 32a, 32b and 32c will be located. In the manufacturing process of the structure 20a, a sacrificial polymer layer is deposited on the substrate 12 and patterned. A film 28 is then deposited around the patterned sacrificial polymer layer.

  Thereafter, the sacrificial polymer layer is removed to form channels 32a, 32b and 32c. The process of depositing and removing this sacrificial polymer layer is described in further detail below.

  Although a square cross section is shown as the cross section of channels 32a, 32b and 32c, the three-dimensional boundary of the channel is a square cross section, a non-square cross section, a polygon cross section, an asymmetric cross section, a curved cross section, an arcuate cross section. A cross-sectional area such as a cross-section, a tapered cross-section, a cross-section corresponding to an ellipse or a part thereof, a cross-section corresponding to a parabola or a part thereof, a cross-section corresponding to a hyperbola or a part thereof, and combinations thereof Can do. However, it is not limited to this. For example, the three-dimensional structure of the channel can be a square structure, a polygonal structure, a non-square structure, a non-square structure, a curved structure, a tapered structure, an elliptical shape or a part thereof, a parabolic shape or There may be a structure corresponding to a part thereof, a hyperbolic shape or a structure corresponding to a part thereof, and a combination thereof, but the present invention is not limited thereto. In addition, the cross-sectional area of the channel may change in spatial height. Further, for example, a plurality of air regions can be connected to each other to form, for example, a microchannel and a microchamber.

  The height of the channels 32a, 32b and 32c can be about 0.1-100 μm, about 1-100 μm, about 1-50 μm and 10-20 μm. Channels 32a, 32b and 32c may have a width of about 0.01 to about 1000 μm, about 100 to about 1000 μm, and about 100 to 300 μm. The lengths of the channels 32a, 32b, and 32c can be widely changed depending on applications and configurations. Channels 32a, 32b and 32c can be in series, parallel, serpentine and other configurations to suit a particular application.

  In one example, the sacrificial polymer used to provide the sacrificial material layer is a slowly degrading polymer that does not cause an excessive pressure increase in the surrounding material when forming the channels 32a, 32b and 32c. can do. In addition, gas molecules generated by the decomposition of the sacrificial polymer are made sufficiently small to permeate the membrane 28. Furthermore, the decomposition temperature of the sacrificial polymer is made lower than the decomposition or decay temperature of the film 28.

  Examples of compounds that can be included in the sacrificial polymer include, but are not limited to, polynorbornene, polycarbonate, polyether, polyester, compounds in which each of these is functionalized, and combinations thereof. The polynorbornene can be an alkenyl substituted norbornene (eg, cycloacrylate norbornene), but is not limited thereto. The polycarbonate can be norbornene carbonate, polypropylene carbonate, polyethylene carbonate, polycyclohexene carbonate, and combinations thereof, but is not limited thereto.

  In addition, the sacrificial polymer can include additional components that alter the processability of the sacrificial polymer (eg, those that increase or decrease the stability of the sacrificial polymer against heat and / or light radiation). . In this regard, examples of the additional component include a photopolymerization initiator and a photoacid initiator, but are not limited thereto.

  The sacrificial polymer can be deposited on the substrate using techniques such as, for example, spin coating, doctor blading, sputtering, lamination, screen or stencil printing, melt dispensing, vapor deposition, CVD, MOCVD or plasma deposition systems. .

  The thermal decomposition of the sacrificial polymer can be performed by heating to the decomposition temperature of the sacrificial polymer and maintaining the temperature for a predetermined time (for example, 1 to 2 hours). The sacrificial polymer breakdown then diffuses through the membrane 28, leaving a hollow structure (channels 32a, 32b and 32c) substantially free of residues.

3B illustrates a membrane 28, a substrate 22, an anode current collector 24, a cathode current collector 26, a first porous catalyst layer 14a, a second catalyst layer 14b, a catalyst layer 34, three channels 32a, A micro fuel cell 20b having 32b and 32c is shown. The chemical composition, dimensions, and characteristics of film 28 may be the same as described for film 12 with reference to FIG. The thickness of the film 28 is measured from the top of the channels 32a, 32b and 32c.

  The substrate 22, the anode current collector 24, the cathode current collector 26, the first porous catalyst layer 14a, the second catalyst layer 14b, and the three channels 32a, 32b and 32c will be described with reference to FIG. 3A. It is the same as what I did.

  The catalyst layer 34 is disposed on the substrate 12 in each channel 32a, 32b, and 32c. In another example, it is not necessary to arrange the catalyst layer 42 in every channel, and the channel in which the catalyst layer is arranged is determined by the desired configuration of the micro fuel cell. The catalyst layer 34 can be a porous layer or a layer with a large surface area. The catalyst layer 34 may cover all of the portion of the substrate that would otherwise be exposed to the fuel in the channels 32a, 32b and 32c, or a smaller area. This may be determined by the desired configuration. The catalyst layer 34 may include a catalyst such as, but not limited to, platinum, platinum / ruthenium, nickel, palladium, their respective alloys, and combinations thereof.

  FIG. 3C shows a micro fuel cell having a membrane 28, a substrate 22, an anode current collector 24, a cathode current collector 26, a second catalyst layer 14b, a catalyst layer 34, and three channels 32a, 32b and 32c. 20c is shown. The chemical composition, dimensions, and characteristics of film 28 may be the same as described for film 12 with reference to FIG. The thickness of the film 28 is measured from the top of the channels 32a, 32b and 32c.

  The substrate 22, the anode current collector 24, the cathode current collector 26, the second catalyst layer 14b, the catalyst layer 34, and the three channels 32a, 32b, and 32c have been described with reference to FIGS. 3A and 3B. Is the same.

  Although the micro fuel cell 20c in this example does not have the first porous catalyst layer, the catalyst layer 34 can cause a catalytic reaction and a catalytic activity.

  FIG. 3D shows a microscopic structure having a membrane 28, a substrate 22, an anode current collector 24, a cathode current collector 26, a first catalyst layer 14a, a second catalyst layer 14b, and three channels 32a, 32b and 32c. A fuel cell 20d is shown. The chemical composition, dimensions, and characteristics of film 28 may be the same as described for film 12 with reference to FIG. The thickness of the film 28 is measured from the top of the channels 32a, 32b and 32c.

  A polymer layer 36 is disposed on the top surface of the film 28 opposite to the substrate 22 side. The second porous catalyst layer 14b and the cathode current collector 26 are disposed on the top surface of the polymer layer 36 opposite to the membrane 28 side.

  The substrate 22, the anode current collector 24, the cathode current collector 26, the second catalyst layer 14b, the first catalyst layer 14a, and the three channels 32a, 32b, and 32c will be described with reference to FIGS. 3A and 3B. It is the same as that. It should be noted that in an example similar to the micro fuel cell 20d, a catalyst layer as described in FIGS. 3B and 3C may be provided.

  The polymer layer 36 is the same as the polymer layer 16 described in FIG. The polymer layer 36 can be the same polymer as described with reference to FIG. 2 and can have the same dimensions. The dimensions of the polymer layer are partially limited by the overall dimensions of the micro fuel cell 20d and the dimensions of the membrane 28.

  So far, the structure 10 having the micro fuel cells 20a, 20b, 20c and 20d has been generally described. Hereinafter, a representative example for manufacturing the micro fuel cell 20a will be described. However, this example can be applied to the manufacture of the micro fuel cells 20b, 20c, and 20d. Note that for clarity, some manufacturing steps are not included in FIGS. Thus, the following manufacturing process is not intended to be exhaustive including all the steps necessary to manufacture the micro fuel cell 20a. Moreover, this manufacturing process is flexible. That is, the manufacturing steps can be performed in a different order than shown in FIGS. 4A-4H, or several steps can be performed simultaneously.

  Note that for clarity, some manufacturing steps are not included in FIGS. Thus, the following manufacturing process is not intended to be exhaustive including all the steps necessary to manufacture the micro fuel cell 20a. Moreover, this manufacturing process is flexible. That is, the manufacturing steps can be performed in a different order than shown in FIGS. 4A-4H, or several steps can be performed simultaneously.

  FIG. 4A shows a substrate 22 on which an anode current collector 24 is disposed. FIG. 4B shows a process of forming a sacrificial material layer 42 on the substrate 22 and the anode current collector 24. The sacrificial polymer layer 42 may be formed using techniques such as, for example, spin coating, doctor blading, sputtering, lamination, screen or stencil printing, melt dispensing, CVD, MOCVD or plasma deposition systems or any combination thereof. Can be deposited on the substrate 10. Further, a mask 38 for removing a part of the sacrificial material layer 42 and exposing the anode current collector 24 is disposed on the sacrificial material layer 42. FIG. 4C shows a process of removing the sacrificial material layer 42 to form the sacrificial portions 44a, 44b and 44c.

  FIG. 4D shows a step of forming the first porous catalyst layer 14a on the sacrificial portions 44a, 44b and 44c. The first porous catalyst layer 14a can be formed by sputtering, vapor deposition, spraying, printing, chemical vapor deposition, or a combination thereof.

  FIG. 4E shows a process of forming a membrane layer 28 on the porous catalyst layer 14 a, the sacrificial portions 44 a, 44 b and 44 c, and the anode current collector 24. The film 28 can be formed using, but is not limited to, spin coating, plasma enhanced chemical vapor deposition (PECVD), chemical vapor deposition, sputtering, evaporation, laser ablation deposition, and combinations thereof. is not. The formation temperature of this film 28 should be about 25-400 ° C, about 50-200 ° C, or about 100-150 ° C. Note that this temperature is limited to a range where other materials are stable (eg, decomposition temperature).

  FIG. 4F shows the process of removing the sacrificial portions 44a, 44b and 44c to form the channels 32a, 32b and 32c. These sacrificial portions 44a, 44b and 44c can be removed by using thermal decomposition, microwave irradiation, UV / visible light irradiation, plasma exposure and a combination thereof. Note that these sacrificial portions 44a, 44b and 44c may be removed at different steps during the manufacturing process, such as after the steps shown in FIGS. 4G and 4H.

  FIG. 4G shows a process of forming the second porous catalyst layer 14b above the channels 32a, 32b and 32c. The second porous catalyst layer 14b can be formed by sputtering, vapor deposition, spraying, printing, chemical vapor deposition, and combinations thereof.

  FIG. 4H shows a process of forming the cathode current collector 26 on the second porous catalyst layer 14b and the membrane 28.

  As described above, a process for adding the polymer layer as shown in FIGS. 2 and 3D is added between the processes shown in FIGS. 4F and 4G, and the second porous catalyst layer and the polymer layer are formed on the polymer layer. A cathode current collector can be formed. This polymer layer can be formed by techniques such as spin coating, doctor blading, sputtering, lamination, screen or stencil printing, melt dispensing, CVD, MOCVD or plasma deposition systems. Also, the step of providing the first porous catalyst layer 14a can be omitted, and the micro fuel cell 20c shown in FIG. 3C can be formed. Furthermore, the catalyst layer 34 (of FIGS. 3B and 3C) can also be placed in some previous steps of forming the membrane layer.

Example 1
A microfabricated fuel cell was constructed and structured on a silicon integrated circuit wafer using a number of processes commonly used in the manufacture of integrated circuits. Such processes include sputtering, polymer spin coating, reactive ion etching and photolithography processes. The proton exchange membrane (PEM) was formed by low temperature plasma accelerated chemical vapor deposition (PECVD) of silicon dioxide. The fuel delivery channel was formed under the PEM and anode catalyst using a patterned sacrificial polymer layer. Platinum-ruthenium catalyst was deposited by direct current (DC) sputtering. The resistance of the oxide film is higher than that of a conventional polymer electrolyte membrane (for example, Nafion (trade name)), but it is thinner.

Experimental Method The construction and manufacture of this micro fuel cell is based on a technique that uses a sacrificial polymer to form a fuel delivery channel for the anode. This sacrificial polymer (Unity 2000P (Promerus, Inc., Brexville, Ohio)) was patterned by exposing it to ultraviolet light to thermally decompose the exposed areas. These patterned portions were covered with a film and an electrode by a sequential forming process. In the final step of this manufacturing process, the patterned portion of the unity is thermally decomposed to leave an encapsulated microchannel (for example, a process similar to the process shown in FIGS. 4A to 4H). The unity pyrolysis was performed by flowing nitrogen uniformly through a Lindberg tube furnace. The final decomposition temperature and time were about 170 ° C. and about 1.5 hours, respectively. The manufacturing process of the micro fuel cell includes a process of depositing the catalyst electrode and the current collector before and after depositing the encapsulating material acting as the PEM. A diagrammatic cross-sectional view of a device formed on an array of parallel microchannels is shown in FIG. 3A.

Silicon dioxide was used as the encapsulating material and PEM. SiO ₂ deposition was performed at a temperature of 60-200 ° C. with a Plasma-Therm PECVD system (Plasma-Therm, St. Petersburg, Fla.). The reaction gas was silane and nitrous oxide, the ratio of N ₂ O: SiH ₄ was 2.25, and the operating pressure was 600 mTorr. Deposition over a period of 60 to 75 minutes resulted in a film thickness of 2.4 to 3.4 μm as measured by an Alpha-Step surface profile meter (KLA-Tencor, San Jose, Calif.).

  The catalyst layer was sputter deposited using a CVC DC sputtering apparatus (CVC Products, Rochester, NY). A platinum / ruthenium target with a 50:50 atomic ratio (Williams Thin-Film Products, Brewster, NY) was used as the source target. FIG. 5 shows the results of an X-ray photoelectron spectroscopy (XPS) scan confirming that the sputter deposited film has equal amounts of two metals. A porous thin film having an average thickness of about 50-200 mm was deposited on the sacrificial polymer and then coated with the film to act as an anode catalyst. In addition, a thick layer of about 600 mm of Pt / Ru was deposited on the bottom of the anode microchannel opposite the membrane side, acting as an additional catalyst and current collector. This additional catalyst improved the performance of the microchannel fuel cell, especially when acidic methanol was used.

  In addition, the porous catalyst cathode was produced by sputtering Pt or Pt / Ru on the top or outside of the PEM. However, one sample cathode was formed by printing a catalyst ink with carbon-supported Pt in Nafion on a PEM, and then coating a gold porous current collector. This thick film approach increased catalyst loading and performance on the cathode side of the PEM. This was particularly useful for studying anode performance by eliminating oxygen reduction at the cathode from the rate limiting step.

All electrochemical measurements including impedance spectroscopy (IS) and linear voltammograms were performed using an electrochemical system from PerkinElner PARSTAT 2263 (EG & G, Princeton, NJ). The scanning speed in the linear sweep voltammetry was 1 mV / s. As in the case of an actual battery, the ionic conductivity was measured by impedance spectroscopy analysis by depositing a SiO ₂ thin film on an aluminum-coated substrate and contacting a mercury probe. The frequency range for impedance measurement was 100 mHz to 1 MHz, and the amplitude of the AC signal was 10 mV. A half-cell device was fabricated comprising a fuel delivery channel and a sputtered catalyst under a SiO ₂ PEM. Instead of the cathode, an epoxy was used to form a well at the top of the device and filled with 1 M sulfuric acid solution. A saturated calomel electrode (SCE) and a Pt wire were placed in this sulfuric acid solution, and measurements were performed as a reference electrode and a counter electrode, respectively. Liquid fuel was supplied and the flow rate was controlled by PHD 2000 Programmable Syringe Pump (Harvar Apparatus, Holliston, Mass.). Hydrogen was supplied from ultra high purity gas in a pressurized tank and passed through a hub for humidification.

Results and Discussion Microfabricated fuel cells have been successfully manufactured using many materials and processes common to integrated circuit manufacturing technology. The performance of this micro fuel cell was measured using different fuels and temperatures for different feature cells, including half cells and full cells. The purpose is to investigate the individual components of the fuel cell (eg anode, cathode and PEM) depending on the processing conditions.

  In addition to catalytic activity, desirable basic properties for the sputtered catalyst layer were porosity and conductivity. The catalyst in contact with the membrane must be porous so that the protons generated during oxidation will contact the PEM and pass to the cathode. Electrons generated in the anode catalyst require a path to the metal current collector. Various amounts of Pt were sputtered onto a substrate having two patterned solid electrodes on either side of the insulator. The sheet resistance of the Pt layer across the space between these electrodes was measured. FIG. 6 shows the measured resistance (Ω / □) of the sputtered Pt thin film and its calculated thickness for a smooth and continuous film as a function of thickness. At values above about 300 cm, the measured and predicted values are consistent, indicating that the membrane was continuous. At values below about 150 mm, the resistance increased dramatically with decreasing thickness. This means that it is the desired porous and discontinuous membrane. Roughening the unity sacrificial polymer surface by RIE increased the amount of metal that could be sputtered prior to forming the solid layer. In this work, a Pt / Ru layer having an average thickness of about 50-200 mm was used as the porous conductive layer on the roughened Unity sacrificial polymer.

It was deposited titanium adhesion layer on top of the Pt / Ru prior to depositing the SiO _2. The amount of Ti required for bonding was minimized. About 45 mm (average thickness) of Ti was deposited between SiO ₂ and Pt / Ru in the sputtered electrode.

Prior to depositing and patterning the Unity sacrificial polymer, sputtering about 600 Å or about 100 μg / cm ² of Pt / Ru yields a relatively solid (non-porous) layer on the substrate, This increased the total amount of anode catalyst in the battery that could be used by the conductive analyte (eg, acidic methanol). This also improved the performance with hydrogen to some extent. The overall results of a battery fabricated to have a Pt / Ru solid layer at the bottom of the microchannel are now described.

The conditions for this proton exchange membrane are different from conventional PEMs (eg, Nafion) because of the mechanical properties and thickness required for microfabricated fuel cells. The SiO ₂ here is shown to act as a stand-alone film. A SiO ₂ film was deposited by PECVD, and ionic conductivity was measured at room temperature by impedance spectroscopy. FIG. 7 is a graph showing the relationship between the deposition temperature and the ionic conductivity of silicon dioxide. As the deposition temperature was lowered, the conductivity increased because the concentration of silanol increased and the density decreased. The conductivity of this thin film was significantly lower than other commonly used PEMs such as Nafion, but was also much thinner than other fuel cell membranes. The sheet resistance of the extruded Nafion membrane (1100 weight equivalent) is 0.1 to 0.35 Ωcm ² . The sheet resistance of a 3 μm thick SiO ₂ film deposited at 100 ° C. is 1200 Ωcm ² at room temperature. Thus, since the resistance is relatively high, the battery voltage at a high current is reduced. The SiO ₂ films used in these devices were sufficient to investigate other parameters such as anode and cathode catalyst loading. These are sufficient for the low current devices used in this study, but in the future we will report on improved SiO ₂ PEM.

A half-cell device was manufactured and tested to evaluate anode performance using various fuels and compared to a full cell test. 8 and 9 show the half-cell test results for hydrogen and methanol, respectively. A solid layer of Pt / Ru was deposited before patterning the sacrificial polymer and before contacting the porous layer on top of the patterned portion with the membrane. The catalyst weight on the membrane surface was 17 μg / cm ² .

  Hydrogen was supplied from ultra high purity gas in a pressurized tank and passed through a hub for humidification. FIG. 8 shows the results when the inlet pressure is 1 to 4 psig (15.7 to 18.7 psia (1 psia = 6894.76 Pa)). The current density of the half-cell varies according to the partial pressure of humidified hydrogen. This indicates that the performance is mainly defined by the catalytic chemical reaction kinetics at the anode, ie proportional to the hydrogen partial pressure. The current density can be further improved by improving the activity of the anode catalyst.

The methanol concentration in water was 1M. The acidic methanol mixture contained 1M methanol and 1M sulfuric acid. FIG. 9 shows the half-cell polarization curves for methanol and acidic methanol. By adding sulfuric acid to the fuel, the solution became conductive to protons. Due to the conductivity of the acidic methanol solution, the active surface area was larger and the current density was improved. By using a Pt / Ru catalyst deposited on the channel wall that is not in contact with the membrane, the amount of methanol oxidation increased. Increasing the flow rate of acidic methanol fuel improves current density and open circuit potential. The main factor that impairs performance at low flow rates appears to be the formation of carbon dioxide bubbles at the anode that must be pushed out of the microchannel. 0.25 (V vs.SCE) from the current density observed (1 mL / hr and 5 mL / respectively hr 2 mA / cm ² and 7 mA / cm ^2), the air bubbles of CO ₂ gas is generated catalytic site It can be seen that the conductivity of protons passing through the fuel from the bottom of the microchannel to the PEM may be limited.

  Fully microfabricated batteries were manufactured and tested with linear voltammetry from open circuit potential at a scan rate of 1 mV / sec. Table 1 shows the main parameters (anode and cathode structure) that affect the battery performance of these power supply devices by contrasting the manufacturing process differences between the five proposed batteries.

FIG. 10 shows the polarization curve (upper) and power curve (lower) for the sample A battery. In Sample A, 31 μg / cm ² of catalyst was provided by sputtering on both the anode and the cathode. Humidified hydrogen with an inlet pressure of 1 psig acting as fuel and oxygen from the air was reduced at the cathode. The performance at 60 ° C. was a measured power density peak of 4 μW / cm ² , more than about 4 times that at ambient temperature conditions. The low current density of these devices with the catalyst sputtered on the cathode compared to the results for the hydrogen half-cell shown in FIG. 7 limits the performance of these devices due to the catalytic activity of the air cathode. It is shown that. This is consistent with the expectation that reducing ambient oxygen at the cathode may limit performance when using pressurized hydrogen at the anode.

  A thick film ink catalyst was deposited on the air inlet cathode to improve catalyst area and activity. Using a catalyst ink printed on top of the membrane significantly increased the performance of the complete cell due to increased cathode catalyst loading. Since the reduction of oxygen at the cathode is significantly improved, it is no longer a limiting electrode. The performance of the cell with the thick film cathode was a function of the anode composition.

FIG. 11 shows the polarization curve (upper) and output curve (lower) for Sample B at ambient temperature, 40 ° C. and 60 ° C. Sample B had the same membrane and anode as Sample A, but used a catalytic ink and gold porous current collector at the cathode. Hydrogen with an inlet pressure of 1 psig was used as fuel, and the cathode was made to be air breathable. The polarization curve at room temperature shows a current density very similar to the result of the hydrogen half-cell of FIG. The performance of sample B was 42 μW / cm ² with a peak power density at 0.23 V and 60 ° C., which was about an order of magnitude higher than for sample A. These two results show that the anode defines the performance of the sample when using a printed catalyst instead of using a catalyst sputtered on the cathode.

  Due to the temperature dependence, a larger power output could be obtained at high temperatures. Waste heat is generated in fuel cells, but the dimensions of these devices and the amount of power generated suggest that they cannot hold enough heat to operate at high temperatures. In the case of an integrated fuel cell, the heat released from the circuit (or other electronic device) incorporating the battery may be used to some extent.

By improving the catalytic activity and surface area of the anode, the current and power density can be further increased. Anode performance was improved by increasing catalyst loading. FIG. 12 shows room temperature polarization curves (upper) and power curves (lower) for three samples with different amounts of catalyst sputtered onto the anode. Hydrogen with an inlet pressure of 1 psig was used as fuel, and the thick film cathode was made air-breathable. Approximately 100 μg / cm ² of Pt / Ru solid layer was deposited on the bottom of each sample microchannel. Sample B had a Pt / Ru of 17 μg / cm ² and Sample C had a Pt / Ru of 34 μg / cm ^{2 at} the membrane surface.

  Sample C had the film sputtered twice as much Pt / Ru as Sample B, but the performance improvement over Sample B was less than 50%. Double the sputtering amount of Pt / Ru does not double the surface area of the catalyst. This is because the deposited islands become larger and a more continuous (less porous) film is formed.

In order to improve electrode performance, it is necessary to increase the surface area of the catalyst, particularly the amount of catalyst in direct contact with the electrolyte. Since a thin layer of SiO ₂ electrolyte is deposited by PECVD, it can be deposited between two catalyst deposits.
Sample D deposits the same 34 μg / cm ² catalyst layer as Sample C on the patterned sacrificial polymer, followed by 400 ＳｉＯ SiO ₂ and an additional 8.5 μg / cm ² additional catalyst layer. After that, a thicker SiO ₂ PEM layer is deposited. Embedding the sputtered second Pt / Ru layer into SiO ₂ increased the catalyst / electrolyte contact area. Sample D only increased the Pt / Ru of the film by 25%, but the peak power density at room temperature of Sample D exceeded 4 times that of Sample C. This significant improvement in current density and power density is due not only to an increase in total catalyst weight, but also to more membrane / catalyst contact due to the SiO ₂ embedded Pt / Ru layer. The two Pt / Ru thin layers and the small amount of SiO ₂ between them form a mixed matrix of catalyst and electrolyte that is conductive to both protons and electrons, and is in contact with the total surface area of the catalyst, especially the electrolyte. Increase the area to be.

The performance of the hydrogen fuel cell was examined as a function of time to see if the data collected by linear voltammetry was consistent with the steady-state value at constant potential. FIG. 13 shows the current density of sample D when held at a constant potential for 10 minutes. This data shows a nearly constant performance very close to the value collected by a linear sweep of 1 mV / s, as shown in FIG. Tests conducted using different devices for longer periods of time, for example several hours, showed similar results. The SiO ₂ film does not swell with water like the Nafion film, and is not easily affected by changes due to time such as a decrease in performance due to drying.

  FIG. 15 shows the polarization and output curves for sample E, a microchannel complete cell with a thick film cathode, when operated at room temperature with an acidic methanol solution at a flow rate of 1 mL / hr. In addition to the porous Pt / Ru in the membrane, a solid catalyst layer at the bottom of the microchannel is used to oxidize the methanol because the fuel solution conducts protons. Although the open circuit potential is lower than when hydrogen is used as the fuel, the peak current and power density are much higher than the same device using hydrogen.

These experiments have shown a tendency to be used to further improve the performance of microformed fuel cells. Adding a catalyst to the bottom of the microchannel is an effective technique when using a conductive fuel. It was also shown that the current density can be increased by increasing the amount of catalyst in the membrane while maintaining the porosity using a plurality of embedded SiO ₂ layers.

The additional areas of this study will also provide an improvement effect on the electrode, such as an increase in anode area, and especially an improvement in the properties of the membrane, which is conductivity. Reducing the thickness of SiO ₂ reduces the resistance of the PEM, but it is necessary to maintain mechanical strength to prevent the fuel cell from being damaged by fuel pressure in the anode microchannel.

It succeeded in manufacture and testing of micro fuel cell using the micro channel and SiO ₂ thin film based on the conclusion sacrificial polymer. This shows that a silicon dioxide film formed by low-temperature PECVD can be used for a thin film integrated device. By reducing the deposition temperature, the conductivity of the film was increased to an acceptable level for the current density obtained by the electrodes used in this study.

By repeating the catalyst sputtering step and the SiO ₂ deposition step to form a catalyst matrix, an electrode having an increased contact area between the catalyst and the membrane catalyst can be obtained. If a conductive analyte such as acidic methanol is used, an additional catalyst not in contact with the membrane can be utilized.

Example 2
A microfabricated fuel cell was constructed and structured on a silicon integrated circuit wafer using a number of processes commonly used in integrated circuit fabrication. Such processes include sputtering, polymer spin coating, reactive ion etching and photolithography processes. As a proton exchange membrane for use in these thin film fuel cells, phosphorous-doped silicon dioxide was studied. Phosphorous doped silicon dioxide is deposited by plasma enhanced chemical vapor deposition (PECVD). The ionic conductivity of such phosphorus-doped silicon dioxide is more than two orders of magnitude higher than the low temperature deposited SiO ₂ used earlier in the microfabricated battery. A film having a thickness of 6 μm and a resistance of 100 kΩ has an area resistance of 60 Ωcm ² , and this value is more preferable than a film having a thickness of 175 μm deposited on Nafion 117. By using phosphorus doped SiO ₂ in the microfabricated fuel cell, improved performance was obtained over conventional cells using undoped silicon dioxide.

Experimental Method The schematic cross section of this microformed fuel cell is similar to that shown in FIG. 3A. The materials and processes used to manufacture the thin film fuel cell have already been described. To form the microchannels, Unity 2000P (Promerus, Brexville, Ohio) was used as the sacrificial polymer. The catalyst layer was sputter deposited using a CVC DC sputtering apparatus (CVC Products, Rochester, NY). A platinum / ruthenium target (Williams Thin-Film Products, Brewster, NY) with an atomic ratio of 50:50 was used as the source target.

The SiO ₂ deposition was performed at a temperature of about 75-250 ° C. in a PECVD system. The reaction gas was silane and nitrous oxide, and the operating pressure was about 600 mTorr. Phosphorus-doped silicon dioxide (P-SiO _2), instead of the standard silane gas (SiH ₄ of 5.0% the He), mixtures of 0.3% phosphine and 5.0% silane in helium carrier gas Deposited by using gas. Typically, the flow rate ratio of PH ₃ / SiH ₄ to N ₂ O (or SiH ₄ to N ₂ 0) was 2.25 and the operating temperature was 100 ° C. For these values, the other parameters were kept the same, and one parameter was changed at a time. Film thickness was measured using an Alpha-Step surface profile meter (KLA-Tencor, San Jose, Calif.) Using a physical mask to prevent deposition on selected areas on the substrate. The deposition of an undoped SiO ₂ PEM layer (some of these data is shown for comparison) used in conventional fuel cell devices was performed using a Plasma-Therm PECVD system (St. Petersburg, Fla. Plasma-Therm). ) And other parameters were made the same at 100 ° C.

Fourier Transform Infrared Spectroscopy (FTIR) was performed using Nicolet model 560 and Omni software. All electrochemical measurements, including impedance spectroscopy (IS) and linear voltammograms, were performed using a PerkinEkner PARSTAT 2263 (EG & G, Princeton, NJ) electrochemical system. The scanning speed of the linear sweep voltammetry was 1 mV / s. Hydrogen was supplied from the ultra-high purity gas in the pressurized tank through the hubra for humidification and supplied to the anode microchannel through a thin tube. The ionic conductivity was measured using impedance spectroscopy by depositing a SiO ₂ thin film on an aluminum-coated substrate and contacting a mercury probe, as in the case of an actual battery. The frequency range for impedance measurement was 100 mHz to 1 MHz, and the amplitude of the AC signal was 10 mV.

On Results and Discussion aluminum-coated glass slides, the _SiO 2 (P-SiO ₂₎ film doped with SiO ₂ film and phosphorus was deposited to a thickness of 1.4～1.5Myuemu. The ionic conductivity of the P—SiO ₂ thin film on the aluminum-coated substrate was measured using impedance spectroscopy (IS). Figures 16 and 17 show the effect of two parameters on conductivity, namely temperature and gas ratio. The data in FIG. 16 was obtained from a sample deposited at 100 ° C. with a power of 400 W, varying only the gas flow rate. The ratio of _{N 2} O with respect to PH ₃ / SiH _4, by decreasing from the standard 2.25 to 1 to 0.5, the conductivity was increased to the ratio becomes slightly 0.5.

FIG. 17 shows that the conductivity of P—SiO ₂ does not depend on the deposition temperature as in the original SiO ₂ film. These films were deposited with a standard gas ratio of 2.25 and an output of 400W. This is a clear basis that the ionic conductivity of P—SiO ₂ was improved by phosphorus rather than an increase in silanol concentration due to a decrease in temperature. The amount of phosphorus does not vary significantly with the deposition temperature. Due to the low decomposition temperature of the PPC sacrificial polymer, a temperature of 100 ° C. is subsequently used for the deposition of P-SiO _{2 in} the fuel cell device.

Conductivity of the P-SiO ₂ film, but significantly increased in comparison with the SiO ₂ undoped, is maintained lower than generally other PEM used as Nafion. However, these are extremely thinner than other fuel cell membranes. The sheet resistance of the extruded Nafion membrane (1100 weight equivalent) is 0.1 to 0.35 Ωcm ² (15). The sheet resistance of a 3 μm thick P—SiO ₂ film deposited at 100 ° C. is 30 Ωcm ² at room temperature. Due to the relatively high resistance, the battery voltage at high current is reduced.

It was compared with SiO ₂ film not doped using P-SiO ₂ thin film as a PEM fine form the fuel cell. Also in this case, the deposition temperature in the PECVD chamber was set to 100 ° C. Ionic conductivity measurements were tested for various manufacturing methods, but the mechanical strength of the membrane at several gas ratios was inferior to that of the standard SiO ₂ manufacturing method. For this reason, in the first fuel cell device doped with phosphorus, silane was simply replaced with phosphine-silane gas using a standard manufacturing method. However, these films are not as strong as the conventional SiO ₂ film and have to be deposited thicker.

A complete microfabricated battery was fabricated using the process described above and tested by linear voltammetry at a scan rate of 1 mV / sec from the open circuit potential. We have successfully used 6 μm thick doped P—SiO ₂ as the PEM for the device. FIG. 18 shows a polarization curve and an output curve of a battery (U-56) in which 150 μm of Pt / Ru is provided on the film surface and a thick film cathode is used. Hydrogen with an inlet pressure of 1 psig was allowed to act as fuel, and the cathode was air-breathable. The results were plotted together with the results from 250 liters of Pt / Ru, which was the double catalyst layer sample (04-28) described above. The open circuit potential at 720 mV was about 70 mV higher. This was probably due to the thicker PEM, which had a positive impact on fuel passage and electrical separation. Since the ionic conductivity was higher than undoped SiO ₂ , the current density does not appear to be reduced by the thicker film. Although the doped sample did not have the catalyst as a whole and was deposited on a portion of the surface, the peak power density was 36 μW / cm ² , about 40% greater than the other samples. The peak power density of both samples was obtained at about 1 mA / cm ² , but the voltage of the doped sample at this current was about 100 mV.

Conclusion The addition of phosphorus to SiO ₂ has been shown to increase the ionic conductivity of the membrane when it is used as a PEM, improving the overall performance of the microfabricated fuel cell. The conductivity of the P-SiO ₂ film deposited under the same processing conditions as the SiO ₂ film conventionally used except for the addition of phosphine gas is about 50 times as large as that of the undoped low-temperature SiO ₂ film. there were. Because of this increase in conductivity, a thicker PEM layer can be deposited to improve the mechanical strength of the device while still reducing the resistance to proton transfer. Such a thicker membrane also improves the open circuit potential and improves overall performance. Performance of P-SiO ₂ samples became those improved than SiO ₂ samples not all of dope containing a sample having a good anode. P-SiO ₂ was found to be preferred thin PEM material for these devices.

  It should be emphasized that the above-described embodiments are merely possible examples of the invention and have been described in order to provide a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments without departing from the principles and spirit of the invention. All such modifications and changes are intended to be included herein within the scope of this invention and protected by the following claims.

FIG. 1 is a diagrammatic cross-sectional view of a typical fuel cell membrane. FIG. 2 is a diagrammatic cross-sectional view of another representative fuel cell membrane. 3A to 3D are diagrams showing four examples of a micro fuel cell. 4A to 4H are schematic sectional views showing a typical manufacturing method of the micro fuel cell shown in FIG. 3A. FIG. 5 is an XPS scan diagram of sputtered platinum / ruthenium (Pt / Ru). FIG. 6 is a graph plotting measured and calculated resistance values of a sputtered platinum film. FIG. 7 is a graph plotting the ionic conductivity of the SiO ₂ film measured by impedance spectroscopy. FIG. 8 is a graph plotting microchannel half-cell performance with humidified hydrogen. FIG. 9 is a graph plotting the performance of a microchannel half-cell when using a methanol-water solution and an acidic methanol-water solution, respectively. FIG. 10 is a graph plotting the performance of a micro fuel cell with a sputtered anode and cathode. FIG. 11 is a graph plotting the performance of Sample B micro fuel cell at various temperatures. FIG. 12 is a graph plotting the performance at ambient temperature of micro fuel cells of Samples B, C, and D having different amounts of sputtered anode catalyst. FIG. 13 is a graph plotting the current density of an embedded catalyst sample held at a constant potential for about 10 minutes. FIG. 14 is a diagram plotting sample D comparing and comparing linear voltammetric polarization data and steady-state data (at 10 minutes) with hydrogen humidified at room temperature. FIG. 15 is a graph plotting the performance of a microchannel fuel cell using 1.0 M acidic methanol at 1 mL / hr. FIG. 16 is a graph plotting the conductivity of the P—SiO ₂ film as a function of gas ratio. FIG. 17 is a graph plotting the conductivity of the P—SiO ₂ film as a function of deposition temperature. FIG. 18 is a graph plotting polarization curves and output curves at room temperature for samples of SiO ₂ doped with phosphorus and undoped SiO ₂ .

Claims (30)

A fuel cell having a membrane comprising a material selected from organic conductive materials, inorganic conductive materials and combinations thereof,
The thickness of this film is about 0.01-10 μm,
The sheet resistance of this film is about O.D. A fuel cell that is 1-1000 Ωcm ² . The fuel cell according to claim 1, wherein
The fuel cell having a thickness of about 0.1 to 5 μm. The fuel cell according to claim 1, wherein
The fuel cell having a thickness of about 0.1 to 2 μm. The fuel cell according to claim 1, wherein
A fuel cell in which the sheet has a sheet resistance of about 1 to 100 Ωcm ² . The fuel cell according to claim 1, wherein
A fuel cell in which the sheet has a sheet resistance of about 1 to 10 Ωcm ² . The fuel cell according to claim 1, wherein
Said material is silicon dioxide, doped silicon dioxide, silicon nitride, doped silicon nitride, silicon oxynitride, doped silicon oxynitride, metal oxide, doped metal oxide, metal nitride, doped metal nitride, A fuel cell selected from metal oxynitrides, doped metal oxynitrides, and combinations thereof. The fuel cell according to claim 6, wherein
A fuel cell wherein the doped silicon dioxide is selected from phosphorous doped silicon dioxide, boron doped silicon dioxide and combinations thereof. The fuel cell according to claim 1, wherein
The fuel cell further includes a catalyst disposed on one side of the membrane,
A fuel cell wherein the catalyst is selected from platinum, platinum / ruthenium, nickel, tellurium, titanium, their respective alloys and combinations thereof. The fuel cell according to claim 8, wherein
The fuel cell further has a polymer layer on the other side of the membrane,
The polymer layer has a catalyst disposed on the opposite side of the membrane side. The fuel cell according to claim 1, wherein
The fuel cell having a thickness of about 0.1 to 2 μm and a sheet resistance of about 1 to 10 Ωcm ² . A substrate on which an anode current collector is disposed;
A film disposed on the anode current collector, the film being silicon dioxide, doped silicon dioxide, silicon nitride, doped silicon nitride, silicon oxynitride, doped silicon oxynitride, metal oxide, doped The material comprises a material selected from metal oxides, metal nitrides, doped metal nitrides, metal oxynitrides, doped metal oxynitrides, and combinations thereof, and the thickness of the film is about 0.01-10 μm. And the film has an area resistance of about 0.1 to 1000 Ωcm ² ;
A hollow channel substantially defined by a portion of the substrate and a portion of the membrane, wherein at least one catalyst layer is exposed to the channel, and the anode current collector is adjacent to the channel The hollow channel being arranged as
A micro fuel cell having a cathode current collector disposed on the opposite side of the membrane from the substrate side,
A micro fuel cell in which a conductive path exists between the catalyst layer and the anode current collector. The micro fuel cell according to claim 11, wherein
The catalyst layer has a first porous catalyst layer disposed on one side of the membrane which is the substrate side of the membrane;
The first porous catalyst layer is exposed in the channel;
A micro fuel cell in which a conductive path exists between the first porous catalyst layer and the anode current collector. The micro fuel cell according to claim 12, wherein
The catalyst layer has a catalyst layer disposed on a substrate exposed in the channel;
A micro fuel cell in which a conductive path exists between the catalyst layer, the first porous catalyst layer, and the anode current collector. The micro fuel cell according to claim 11, wherein
The catalyst layer includes a catalyst layer disposed on a substrate exposed in the channel;
A micro fuel cell in which a conductive path exists between the catalyst layer and the anode current collector. The micro fuel cell according to claim 11, wherein
The fuel cell further includes a second porous catalyst layer disposed on the side of the membrane opposite to the substrate side,
A micro fuel cell in which a conductive path exists between the second porous catalyst layer and the cathode current collector. The micro fuel cell according to claim 15, wherein
The micro fuel cell further includes a polymer layer disposed on the side of the membrane opposite to the substrate side,
A micro fuel cell in which the cathode current collector and the second porous catalyst layer are disposed on the polymer layer. The micro fuel cell according to claim 16, wherein
A micro fuel cell, wherein the polymer layer is selected from perfluorosulfonic acid / polytetrafluoroethylene copolymer, polyphenylene sulfonic acid, modified polyimide, and combinations thereof. The micro fuel cell according to claim 11, wherein
The micro fuel cell, wherein the catalyst layer includes a catalyst selected from platinum, platinum / ruthenium, nickel, tellurium, titanium, alloys thereof, and combinations thereof. The micro fuel cell according to claim 11, wherein
The thickness of the film is about 0.1-5 μm,
A micro fuel cell in which the sheet has a sheet resistance of about 1 to 100 Ωcm ² . A method for manufacturing a micro fuel cell, comprising:
Providing a substrate on which an anode current collector is disposed;
Disposing a sacrificial polymer layer on the substrate and the anode current collector;
Removing a portion of the sacrificial polymer material not disposed on the anode current collector to form a sacrificial material portion;
Disposing a first porous catalyst layer on the sacrificial material portion;
Disposing a layer of membrane material over the sacrificial material portion, the first porous catalyst layer, and the anode current collector, the membrane material comprising silicon dioxide, doped silicon dioxide, silicon nitride Doped silicon nitride, silicon oxynitride, doped silicon oxynitride, metal oxide, doped metal oxide, metal nitride, doped metal nitride, metal oxynitride, doped metal oxynitride and these The process to be selected from the combination;
A method for manufacturing a micro fuel cell, comprising: removing the sacrificial material portion to form a hollow channel substantially defined by the substrate, the membrane material, and the first porous catalyst layer. The method of manufacturing a micro fuel cell according to claim 20,
Disposing a second porous catalyst layer on the top of the membrane material opposite the substrate side;
And a step of disposing a cathode current collector in a part of the second porous catalyst layer. The method of manufacturing a micro fuel cell according to claim 20,
The method for manufacturing the micro fuel cell further includes:
Disposing a polymer layer on the membrane material;
Disposing a second porous catalyst layer on top of the polymer layer opposite the layer side of the membrane material;
Disposing a cathode current collector on a part of the second porous catalyst layer. The method of manufacturing a micro fuel cell according to claim 20,
A method for producing a micro fuel cell, wherein the polymer layer is selected from perfluorosulfonic acid / polytetrafluoroethylene copolymer, polyphenylenesulfonic acid, modified polyimide, and combinations thereof. The method of manufacturing a micro fuel cell according to claim 20,
Providing a catalyst layer on a part of the substrate,
A method for manufacturing a micro fuel cell, wherein the catalyst layer is disposed on a portion of the substrate between the sacrificial material portion and the substrate. The method of manufacturing a micro fuel cell according to claim 20,
A method for producing a micro fuel cell, wherein the sacrificial material is selected from polyimide, polynorbornene, epoxide, polyarylene ether, polyarylene, inorganic glass, and combinations thereof. A method for manufacturing a micro fuel cell, comprising:
Providing a substrate on which an anode current collector and a catalyst layer are disposed, the anode current collector and the catalyst layer being adjacent to each other;
Disposing a sacrificial polymer layer on the substrate, the anode current collector and the catalyst layer;
Removing a portion of the sacrificial polymer material not disposed on the anode current collector to form a sacrificial material portion on the catalyst layer;
Disposing a layer of film material over the sacrificial material portion and the anode current collector, the film material being doped with silicon dioxide, doped silicon dioxide, silicon nitride, doped silicon nitride, silicon oxynitride, doped The process of selecting from silicon oxynitride, metal oxide, doped metal oxide, metal nitride, doped metal nitride, metal oxynitride, doped metal oxynitride and combinations thereof;
A method of manufacturing a micro fuel cell, comprising: removing the sacrificial material portion to form a hollow channel substantially defined by the substrate, the membrane material, and the catalyst layer. In the manufacturing method of the micro fuel cell according to claim 26,
The method for manufacturing the micro fuel cell further includes:
A method for manufacturing a micro fuel cell, comprising a step of disposing a first porous catalyst layer on the sacrificial material portion before disposing the membrane material. In the manufacturing method of the micro fuel cell according to claim 26,
The method for manufacturing the micro fuel cell further includes:
Disposing a second porous catalyst layer on the top of the membrane material opposite the substrate side;
And a step of arranging a cathode current collector in a part of the second porous catalyst layer. In the manufacturing method of the micro fuel cell according to claim 26,
The method for manufacturing the micro fuel cell further includes:
Disposing a polymer layer on the membrane material;
Disposing a second porous catalyst layer on top of the polymer layer opposite the layer side of the membrane material;
And a step of disposing a cathode current collector on a part of the second porous catalyst layer. In the manufacturing method of the micro fuel cell according to claim 26,
A method for producing a micro fuel cell, wherein the polymer layer is selected from perfluorosulfonic acid / polytetrafluoroethylene copolymer, polyphenylenesulfonic acid, modified polyimide, and combinations thereof.

Images